Otsego Lake is a productive water body classified as being in the mid to late stages of mesotrophy (moderately productive). The shallow depth of the lake enhances prospects for maintaining present water quality. However, the low buffering capacity and long water retention time of the lake increases the influence of pollutants upon water quality. The lake is well-suited for warm water fisheries and supports healthy populations of game fish. However, the dominant algae in the lake are blue-green which appears in blooms throughout the summer. Under oxygenated conditions, the bottom sediments are capable of adsorbing large quantities of phosphorus and function as a phosphorus sink. Laboratory experiments demonstrate that the sediment will release high concentrations of phosphorus during anaerobic periods. The lake is fed by groundwater that enters along the western and northern shore and drains through the ground towards the North, East and Main Branches of the AuSable River. Shoreline pollution is more evident along the west shore than the east shore, in agreement with expected groundwater movements. Water quality in all the canals is much worse than the water quality of the lake.